This invention relates to implantable drug infusion pumps. In particular, this invention relates to a method and apparatus for controlling drug dosages that can be delivered by an implantable drug infusion pump.
Implanted infusion pumps deliver therapeutic drugs to a patient according to a computer program executed by a processor that is programmed with drug dosing parameters. A microprocessor controls a small, positive displacement pump according to programming instructions delivered to the microprocessor through an RF programming link so as to permit the implantable pump to be remotely programmed and operated. In the course of executing its program, the processor controls a mechanical pump according to programmed dosage parameters.
A problem with prior art drug infusion pumps are that they run open-loop, i.e. there is no feedback mechanism controlling drug dosing. Moreover when used for treating many disorders, implantable infusion pumps need to permit the patient to self-administer a bolus of medication on demand. For example, many diabetics need to administer a bolus of insulin either just prior to or just after a meal. The changing of drug infusion rates is important as the insulin requirements of diabetic patients"" change during the course of a day. Therefore, it is important that any drug treatment system be able to accommodate a predetermined constant delivery rate as well as any adjustments that may be required during the course of a day. However, this frequent changing of dosage rates can lead to potential underdosing or overdosing situations.
While prior art implantable and programmable infusion pumps permit a patient to administer additional drug dosages on demand, these prior art devices do not adequately control the amount of patient-administered dosages increasing the likelihood that a patient may overdose or underdose himself, adversely affecting the patient""s physician-prescribed therapy.
A remotely programmable and implantable tissue stimulator is disclosed in U.S. Pat. No. 5,443,486 to Hrdicka et al., for a xe2x80x9cMethod and Apparatus to Limit Control of Perimeters of Electrical Tissue Stimulators.xe2x80x9d While the ""486 Patent discloses a remotely programmable tissue stimulator and permits the patient to control the administration of tissue stimuli, the device disclosed in the ""486 patent does not provide for programmable drug infusion therapy. Nor does the ""486 provide for software-based drug infusion limits.
Programmable infusion limits in implantable infusion pumps might lessen the likelihood that a patient will overdose or underdose himself. Moreover, a software-defined limit might also lessen the likelihood that certain drug regimens will be used improperlyxe2x80x94even by health-care providers. By using a software-defined drug dosage limit, pump manufacturers might specify certain maximum and minimum dosages for certain disorders by pre-programming their own infusion pumps with the drug dosage limitations.
In order to lessen or prevent inadvertent infused drug overdoses or underdoses, implanted drug infusion pumps require limits to be placed upon the drug delivery amount and/or frequency by health care professionals. An internal limit on the amount by which a patient can self-dose a drug, would be an improvement over the prior art implantable infusion pumps. Similar limits might prevent health care providers from inadvertently overdosing, or even underdosing treatments.
A fully implantable drug infusion pump, which includes an RF programming link, an implantable drug reservoir wherein a therapeutic drug is stored and a small, microprocessor-controlled positive displacement pump is entirely software controlled using an embedded and implantable microprocessor and power supply. Programming instructions and data delivered to the microprocessor through an RF programming link are used to limit infused drug dosage. The dosage limit data is stored in programmable memory within the microprocessor or in separate memory devices. The microprocessor controlling drug administration compares the amount of drug administered over time according to the data parameters defining the treatment regimen""s dosage limits.
In the preferred embodiment of the invention, the programmable infusion pump also permits the patient to self-administer additional doses on demand. The patient-requested additional dosage limits are specified by the patient""s health care provider and these limits can be programmed into the implantable pump by the health care provider using the RF programming link. Thereafter, access to the dosage limits is not available to the patient. RF programming, data encryption or other security software could limit access to the drug dosage limit data. Within the therapy program limits, patients would have the flexibility to adjust the delivery of dosages to account for meals or needed bolus flow rates during the course of the day. These changes to the base flow would be tracked by a therapy program and compared to the dosage limits. Patient notification, for example through an alarm, may be utilized if the actual dosage would fall above or below the programmed dosage limits. Patient-controlled drug dosage is limited by the health care provider-specified limit value.
In another embodiment, drug manufacturers, as well as health-care providers, might offer implantable infusion pumps for use with certain drugs that have precise treatment regimens. Over-dosing or under-dosing might be precluded by way of dosing definitions programmed into secure data storage locations.
In yet another embodiment, underdosage by the patient could be avoided if the pump is programmed to a minimum dosage or by warning the patient. The warning could be an audio alarm from the pump or an indicator on the patient""s controller to which the patient could respond by increasing the dosage.
The same underdosage alarm could be implemented to alert the patient of a requested overdosage, thereby alerting the patient when a dosage request amounts to an overdosage not allowed by the pump.